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Issued February 14, 1914. 

U. S. DEPARTMENT OF AGRICULTURE, 
FOREST SERVICE, 

HENRY S. GRAVES, Forester. 



FORE"' " TREE DISEASES COMMON 
IN CALIFORNIA AND NEVADA. 



A MANUAL FOR FIELD USE. 



BY 

E. P. MEINECKE, 

Forest Pathologist, Bureau of Plant Industry. 



WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 

1914. 



Issued February 14, 1914. 

U. S. DEPARTMENT OF AGRICULTURE, 

- FOREST SERVICE, 

HENRY S. GRAVES, Forester. 



FOREST TREE DISEASES COMMON 
IN CALIFORNIA AND NEVADA. 



A MANUAL FOR FIELD USE. 



BY 
E. P. MEINECKE, 

Forest Pathologist, Bureau of Plant Industry. 



WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 

1914. 






.XC75" 
W4r 



D. OF D, 

MAS 4 1914 




CONTENTS 



Page. 

Scope of the study 7 

Structure of the tree 8 

Normal functions of the tree 9 

Disease a disturbance of normal functions 11 

Causes of disease 12 

Examination of diseased trees 17 

Symptoms of disease 18 

Fungi 24 

Nature and development 24 

Fungi with fruiting bodies in the form of stools or crusts. 29 

Porous fungi 29 

Spiny fungi 29 

Gill-bearing fungi 30 

Fungi with fruiting bodies not in the form of stools or 

crusts 30 

Leaf and twig fungi 30 

Attack on vital and nonvital parts of the tree 30 

Fungi which attack vital parts of the tree 30 

Fungi which attack nonvital parts of the tree 31 

Diseases of foliage, twigs, and branches 32 

Effect 32 

Needle disease of white and red fir 33 

Tar-spot fungus 33 

Needle fungus of lodgepole pine 33 

Needle disease of yellow pine 34 

Stunting needle fungus of yellow and Jeffrey pine 34 

Yellow witches' brooms of white and red fir 35 

Incense cedar rust 35 

Blue witches' brooms of sugar pine 37 

Tip-dying of white and Douglas fir 37 

Black cobweb fungi 38 

Pine gall fungus 38 

3 



4 CONTENTS. 

Page. 

Diseases of roots, trunks, and limbs 40 

Effect 40 

Root fomes 42 

Ring-scale fungus 43 

Chalky quinine fungus 44 

Sulphur fungus 45 

Incense cedar dry rot 46 

Polyporus schweinitzii 47 

Red-belt fomes 47 

Polyporus dryophilus 48 

False tinder fungus 49 

White pouch fungus 50 

Indian paint fungus 50 

Hydnum erinaceus 52 

Honey fungus 52 

Scaly lentinus 53 

Mistletoe 54 

Control of disease 58 



ILLUSTRATIONS. 



Page. 

Plate I. Fungus gall on western yellow pine 64 

II. Daedalea quercina on oak railroad tie 64 

III. Gill-bearing fungus 64 

IV. Trametes pini fruiting bodies on shortleaf pine 64 

V. Trametes pini fruiting bodies on lodgepole pine ... 64 

VI. Ring scale in lodgepole pine caused by Trametes 

pini 64 

VII. Chalky quinine fungus fruiting body on Douglas fir. 

VIII. Chalky quinine fungus in lodgepole pine 64 

IX. Cluster of sulphur fungus fruiting bodies 64 

X. Sulphur fungus rot in the heartwood of oak 64 

XI. Fully developed fruiting body of incense cedar dry- 
rot fungus 64 

XII. Incense cedar wood with dry rot 64 

XIII. Fresh fruiting body of Polyporus schweinitzii 64 

XIV. Fruiting bodies of red-belt fomes on western hem- 

lock 64 

XV. False tinder fungus fruiting bodies on aspen 64 

XVI. Indian paint fungus fruiting body on noble fir 64 

XVII. Indian paint fungus fruiting bodies, showing spiny 

undersides 64 

XVIII. Indian paint fungus in white fir 64 

XIX. Honey fungus fruiting bodies on oak 64 

XX. Honey fungus in oak 64 

XXI. Mistletoe on incense cedar 64 

XXII. Mistletoe on lodgepole pine 64 

XXIII. Witches' brooms on yellow pine caused by mistle- 

toe 64 

XXIV. Witches' brooms on lodgepole pine caused by mis- 

tletoe 64 

5 



FOREST TREE DISEASES COMMON IN CALI- 
FORNIA AND NEVADA. 



SCOPE OF THE STUDY. 

This manual, designed for practical use in the field, 
discusses only the more important tree diseases found 
in California and parts of Nevada, though most of 
them are common also in other forest regions. Its aim 
is to enable the field man to determine the cause of the 
commoner diseases and injuries and to understand their 
effect on the living tree. It discusses also ways and 
means of control of fungi and mistletoes, as well as 
climatic, biological, and soil conditions which bring 
about diseases in forest trees. 

In studying forest tree diseases the object is of 
course to learn how to fight and control them. For 
success in this, however, we must at least know the 
more common forms of the enemies we are to deal with, 
how they act on the living tree, which organs they 
attack, how they do it, and what the consequences are. 
The simplest case of injury is destruction of certain 
parts of the tree, when, for instance, a few needles are 
browsed off by sheep or killed by needle miners or a 
fungus. In such cases the tree will hardly suffer, and 
there is no reason to speak of disease. If, however, 

7 



8 FOREST TREE DISEASES. 

a great number of needles are destroyed the regular 
life functions of the tree are affected and it becomes 
diseased. With trees, as with animals, the various life 
functions are confined to certain organs, and anything 
which affects the health of these affects the functions as 
well. Disease is an unbalancing of normal functions, 
and to understand its nature we must first understand 
these functions and their relations to each other. 

STRUCTURE OF THE TREE. 

Trees grow in length in the youngest (end) part of 
the twigs and at the very ends of the roots; they grow 
in thickness in the so-called cambium, a very thin layer 
of cells between the bark and the wood of roots, stem, 
and branches. The cells of the twig ends, of the root 
tips, and of the cambium are capable of division, and 
certain young cells produced by this division, if properly 
nourished, grow to normal size, divide in turn, and so 
on. The growth in thickness (diameter) by the cam- 
bium takes place only in spring and early summer, and 
results in the production of a thin layer of wood all 
over the tree. In cross section this layer appears in the 
shape of the so-called annual ring, corresponding to one 
year's growth in diameter. The springwood of the an- 
nual ring is light and soft; the summerwood appears 
as a narrower, darker line and is harder than the other. 

After a number of years the cells of the oldest an- 
nual rings of wood die and, after undergoing chemical 
changes, form what is called the heart wood. The liv- 
ing wood outside of the heartwood is called sapwood. 



NOKMAL FUNCTIONS. 9 

Only the inner portion of the bark, adjoining the sap- 
wood and separated from it by the very thin cambium, 
is living; the outer portion consists of an impermeable 
skin or layer of cork or cork scales. The thicker these 
layers of cork scales the better protection they offer the 
living tissues from fungi and mistletoes, but not from 
insects. 

NORMAL FUNCTIONS OF THE TREE. 

All plants with green leaves or needles contain a 
green pigment which enables them to live on the very 
simplest food. They take up water and mineral salts 
through the roots and carbon dioxide and oxygen 
through the leaves ; with help of the green pigment the 
plants produce under the influence of sunlight from 
these chemically simple materials the bulk of the chemi- 
cally very complex substances of which they are built 
up. This function can be carried on only in sunlight. 
Animals and fungi, on the contrary, live on chemically 
very complex food, which they break up into simpler 
substances. 

Large quantities of water containing comparatively 
little mineral salts are taken up by hairs on the very 
tips of the roots, which have to be continually renewed. 
Older roots take no part in this pumping of water 
from the ground. Their role is to anchor the plant in 
the soil. The roots, if not too old, also breathe to a cer- 
tain extent; that is, they take oxygen from the air in 
the soil. 

The water with the mineral salts is pumped through 
the roots and then through the trunk in the sapwood 



10 FOREST TREE DISEASES. 

upward to the leaves or needles. Enormous quantities 
of water are given off by the foliage in transpiration. 
The mineral salts accumulate and are utilized for vari- 
ous purposes. 

The green leaves have three distinct functions — 
transpiration of water and its regulation, breathing 
(respiration), and assimilation of carbon dioxide. 

Transpiration of water takes place through innu- 
merable small openings in the leaves, which regulate to 
a certain degree the quantity of water thus given off. 

Every plant breathes (respires) exactly as every ani- 
mal does; that is, oxygen is taken up and carbon di- 
oxide, the product of respiration, is discarded. This 
process goes on day and night, exactly as in the case of 
animals. 

Carbon dioxide (a gas consisting of carbon and oxy- 
gen) from the atmosphere is assimilated by green leaves 
under the influence of sunlight. The carbon from the 
carbon dioxide, together with the water and mineral 
salts brought up from the roots, is used in the forma- 
tion of chemical substances of highly complex nature 
(starch and sugar) ; the oxygen from the same source is 
exhaled. In the leaves also takes place the assimilation 
of nitrogenous salts and formation of albumen. 

Starch, sugar, and albumens furnish food for the 
growing cells of the cambium and the root tips, being 
transported from the leaves, where they are formed, 
downward through the living bark. The surplus above 
the amount consumed is stored. 

All these functions must be perfectly balanced. The 
development of the root system, for instance, which sup- 



DISEASE A DISTURBANCE. 11 

plies the water and mineral salts, is not independent of 
the development of the foliage. Both are correlated, 
and one must not overbalance the other. 

DISEASE A DISTURBANCE OF NORMAL FUNCTIONS. 

All diseases, properly speaking, can be traced to some 
interference with the normal functions just described 
and the economic equilibrium established in a sound 
tree. 

Leaf diseases, by killing a greater part of the foli- 
age, destroy the very organs in which food for the 
growing tissues of the tree is prepared. The cambium 
does not receive proper nourishment and can not grow, 
while the hairs on the root tips, which must be renewed 
continually, are no longer developed for lack of food, 
with the result that when once the surplus of food in 
storage in the wood is also exhausted no more water is 
pumped up to the remaining leaves. 

Diseases of the bark of branches and trunk intercept 
the flow of food coming down in the bark from the 
leaves. The result is starvation of cambium and roots. 
This explains how damage is done by mistletoes, by 
Peridermium and other bark-destroying fungi, and by 
bark beetles. The effect is the same as girdling the 
tree with an ax. The bark also stores reserve mate- 
rials, which are eliminated by the disease. 

Diseases of the sapwood cut off the water supply 
which is pumped upward from the roots in the living 
sapwood to the upper parts of the tree, and the leaves 
suffer or die of drought. Any reserve materials stored 
in the sapwood are lost to the tree. 



12 FOREST TREE DISEASES. 

Diseases of the root system have the same disastrous 
effect on the water supply of the tree, and destroy the 
reserve materials stored in the roots. 

Diseases of the flowers and seeds destroy the faculty 
of reproduction. 

CAUSES OF DISEASE. 

Whenever a tree, growing under the same conditions 
as its thrifty neighbors, appears in any way unhealthy, 
there is reason to assume some kind of attack by para- 
sitic fungi, mistletoes, or insects. Yet there are quite a 
number of other things which bring about disease or 
death in trees, and before we decide finally that one of 
the three factors named is responsible, except of course 
where there can be no possible doubt, we should first 
make sure that there is not some other cause for the 
abnormal condition of the tree in question. Parasites 
are plants or animals which live off the living tissues of 
other plants or animals, not merely by mechanically 
destroying them, but by partly or totally penetrating 
the tissues of the so-called " host " — that is, the plant 
or animal they live on. Certain parasites are able to 
enter the youngest parts of trees, twigs, or leaves 
directly; the majority of fungi causing decay of the 
wood can get into the interior of the living tree only by 
way of a pin knot or a wound. For this reason every 
wound caused by lightning, by fire, by man, or by ani- 
mals constitutes a menace of infection, unless it receives 
an aseptic dressing such as the coniferous trees to a 
certain extent give in covering the exposed surface with 
resin. 



CAUSES OF DISEASE. 13 

Smaller wounds in pines are, as a rule, soon covered 
over by pitch, which very effectively prevents the dry- 
ing out of the exposed sapwood and the germination 
and growth of fungus spores. The less resinous coni- 
fers and our broadleaf trees lack this protection, and 
even the pines are unable to cover very large wounds 
completely. The sapwood dies, dries out, and checks. 
Spores (p. 28) of parasitic fungi enter the cracks, ger- 
minate, and infect the heartwood. Proper moisture 
and temperature are the necessary conditions for ger- 
mination of the spores; but infection can only take 
j)lace if the spores land where the mycelium resulting 
from germination finds the proper food for further 
development. The spore of a heartwood-inhabiting 
fungus, such as Polyporus amarus, for instance, must 
be carried on to an incense cedar, since the fungus can 
not attack any other tree. If it lands on the bark it 
may germinate, but the resulting mycelium is unable 
to penetrate into the heartwood. Only when a spore is 
deposited on a broken-off branch stub, which allows the 
mycelium to grow through it into the heartwood of 
the bole, or when a spore falls onto an open wound 
large and deep enough to offer an entrance into the 
heartwood either directly or through cracks, can infec- 
tion take place. Thus certain diseases of the heartwood 
(rot or decay) can very frequently be traced directly 
to fire scars, lightning scars, spike tops, stubs of 
broken limbs and branches^ and even to the crotches of 
forked trees, where the swaying of the two forks in the 
wind mechanically destroys the tissues. Moisture nat- 



14 FOKEST TREE DISEASES. 

u rally gathers here, and spores find the most favorable 
conditions for germination. 

Resin is not the only means of natural protection. 
All trees have the faculty, though in varying degrees, 
of healing over wounds and growing over pin knots and 
stubs. This is, of course, a very slow process, and the 
tree is subject to infection until it is completed. 

Purely mechanical destruction is not disease, but it 
may produce disease. Porcupines, for instance, will 
live off the tender bark of young pines (Jeffrey pine, 
lodgepole pine) when the snow is too deep for them to 
get any other food. As long as they destroy only small 
patches of living bark no material damage is done. In- 
significant injury caused by mechanical destruction of 
small parts of vital organs is soon overcome in a healthy 
tree ; the remaining sound tissues simply take over the 
surplus work to be done — they work " overtime." But 
when not enough bark remains to perform the functions 
required of it, all parts of the tree above the point of 
attack soon show signs of suffering. The same holds 
true for insects. A tree scarcely suffers from the attack 
of isolated insects ; but when they appear in great num- 
bers and practically girdle the trunk the tree is seri- 
ously injured. 

Mechanical destruction is brought about by man, by 
animals, by lightning, fire and storm, cloudbursts, heavy 
snowfall, etc. Carelessness in felling timber, removal 
of bark for roofing of cabins, unnecessary and extrava- 
gant blazing, tapping of Jeffrey pine for resin and 
abietene are only a few examples of the destructive ac- 



CAUSES OF DISEASE. 15 

tivity of man in the forest. Insects destroy the foliage, 
fruit, bark, or wood. Porcupines, deer, cattle, sheep, 
and other mammals partly live off the green bark, 
partly browse off the foliage. Rodents sometimes in- 
jure the roots, particularly of very young trees. 

Lightning will not in every case kill the tree it 
strikes. As a rule, however, its effect is only realized 
when a heavy discharge strikes a tree and injures it 
very severely. But when, as in most cases, the elec- 
tricity discharged over a forest is divided into a num- 
ber of weaker currents, which strike as many dominant 
trees, each of which acts as a conductor, the effect on 
the single tree becomes less apparent and is easily over- 
looked. Lightning is very often the cause of spike tops 
(in case of white firs see also p. 57). Grooves and 
streaks on the bark and smaller Avounds caused by 
lightning are very common. 

The effects of fire are too well known to need de- 
scription. It should be remembered ; however, that 
often a tree may appear green and healthy for as long 
as two or three years after a fire, only to succumb at 
last to the injuries received. Decay in very many cases 
is directly traceable to old fire scars; in fact, fire as a 
cause of wounds is responsible for more cases of heart- 
rot than all other factors taken together. The charred 
surface of exposed wood in the beginning affords pro- 
tection to the wood underneath it, but soon the charcoal 
is partly worn off, and the sapwood, which is no longer 
protected by the bark, dies and checks, thus offering 
an easy entrance to the germinating spores of wood- 
destroying fungi. 



16 FOREST TREE DISEASES. 

Heavy storms may injure a tree in various ways. 
Tops or limbs or the trunk are broken off. Sometimes 
part of the roots of a tree which is poorly anchored in 
the soil may be torn off and the tree completely up- 
rooted and blown over. In falling such trees fre- 
quently injure their neighbors. 

When a cloudburst displaces the ordinary bed of a 
mountain stream, any trees caught in the torrent, even 
if they withstand the pressure of the water, suffer more 
or less from the action of rolling bowlders, which rub 
off the bark, and later from the changes brought about 
in their life conditions by the thick layer of debris left 
after the stream has receded. 

Other causes of disease are smelter fumes and smoke, 
frost, sunscald, drought, and excess of water in the soil. 
In the neighborhood of smelters and other large indus- 
trial plants which burn great quantities of coal the for- 
ests, particularly in the direction of the prevailing 
winds, are often very seriously injured by the poison- 
ous gases escaping either from the ore or from the coal 
used. 

Winter frost sometimes causes long internal cracks 
in older forest trees, often corresponding to rather con- 
spicuous perpendicular ridges on the outside of the 
trunk. Late frosts are likely to kill young shoots (see, 
however, white fir, p. 37). In long, dry winters the 
foliage of coniferous trees is often stimulated on 
warmer days to transpiration of water, which the root 
system is not able to restore from the frost-bound soil. 
The needles then die and turn red. 



EXAMINATION OF DISEASED TREES. 17 

Sunscald is common on thin-barked trees, particu- 
larly after sudden exposure to strong sunlight by thin- 
ning, snowbreak, etc. 

Heavy snowfall often causes serious damage by bend- 
ing and breaking young trees or branches, or by favor- 
ing the development of certain fungi {H erpotrichia 
nigra). 

EXAMINATION OF DISEASED TREES. 

The nature of a disease can be determined only by 
keeping in mind all the possible factors which make 
for disease (see "Causes of disease," p. 12), and the 
way they affect the functions of the normal tree (see 
"Disease a disturbance of normal functions," p. 11). 
By taking into consideration all possibilities and by 
discarding everything that does not suit the particular 
case we finally arrive at a comparatively small group 
from which by careful examination we will as a rule 
be able to choose the correct answer to our problem. 
It should be remembered, however, that a disease is 
not always encountered under its most typical aspect. 
A tree attacked by a fungus may show signs of suffer- 
ing, but the fungus itself may not yet be sufficiently 
developed to form fruiting bodies (p. 25). In other 
cases the fruiting bodies may be very small, very in- 
conspicuous, or hidden on the roots or under the bark. 
The fruiting bodies of certain fungi even vary con- 
siderably with host and climate (Pis. IV and V). Ex- 
amination of diseased trees, therefore, can not be too 
careful. 

50977°— 14 2 



.18 FOREST TREE DISEASES. 

No age is free from disease; but certain diseases are 
confined to definite ages. Some fungi, for instance, 
only attack young reproduction or branches and twigs 
in the same youthful stage of development. Others are 
confined to mature and overmature trees. 

Few implements are required for the examination of 
diseased trees. A hatchet or an ax is sufficient for 
opening up the bark or outer layers of wood. A pick 
and shovel are needed when the seat of the disease 
seems to be in the root system. Whenever parts of the 
trunk, branches, or the root system are affected or 
killed, it is important to find out the extent of the 
disease and, if possible, to follow any abnormal signs 
to their source. For the examination of the foliage an 
ordinary magnifying glass will do in most cases. 

SYMPTOMS OF DISEASE. 

The foliage being the most sensitive visible organ, its 
general aspect is a valuable index of the health of a 
tree. When the foliage of a coniferous tree, for ex- 
ample, appears to be diseased, and no other cause, such 
as drought, girdling, smelter fumes, or recent fire, can 
be found, the needles should be held to the light to see 
whether they are hollowed out by needle miners, the 
larvae or pupaa of which may at certain times be found 
inside them. Partial or total destruction of the needles 
or leaves is due to broAvsing by mammals or to cater- 
pillars and the larva- of sawflies. We may also find the 
fruiting stage of a fungus in the shape of small black 
spots or narrow black lines on discolored parts of the 



SYMPTOMS OF DISEASE. 19 

leaf or needle. Often the fruiting bodies develop only 
on the underside of the needles or leaves. 

Premature dying of the foliage of tops, limbs, 
branches, or twigs may be an indication of local inter- 
ference with the water supply, the result of partial or 
complete girdling by porcupines and other mammals 
(deer, cattle, sheep) or by insects. Leaf or twig inhab- 
iting fungi may, however, locally attack the foliage. 
Lightning sometimes kills limbs. On old yellow pines, 
for instance, it is often possible to follow the track a 
discharge of lightning has taken down the tree by the 
limbs it has killed on its way. Dead limbs may also be 
an outward sign of some local trouble in the root 
system. 

Partial or total dying (reddening, yellowing, pre- 
mature dropping) of the foliage of single trees may be 
caused by* a variety of agencies, but can, except in the 
case of needle miners and certain needle fungi, almost 
invariably be traced to some interference with the water 
supply. If the tree dies in a comparatively short time, 
the probabilities are that the trouble is located at the 
butt or in the root system. It is frequently, but not 
always, a sign of attack by bark beetles. 

When the foliage of practically all the trees in a 
stand is affected at the same time it indicates that 
the leaves or needles may have been poisoned by smelter 
fumes or similar gaseous products or killed by fire. It 
may also mean invasion by insects or that the water 
supply is in some way out of order (winter injury, 
p. 16). 



20 FOREST TREE DISEASES. 

Disturbances of the root functions caused by drought 
or by an excess of water in the soil, total or partial 
destruction of the roots by parasitic fungi, insects, 
rodents, etc., or starvation of the root tips caused by 
diseases or destruction of the living bark above by 
fungi, insects, porcupines, etc., all tend to cut off the 
water supply of the tree, the results of which are felt 
first in the needles or leaves. Certain winter conditions 
have the same effect (see p. 16). Resin flow at the butt 
of the tree frequently indicates root disease. 

When twigs appear to be diseased examination should 
be made of the part of the twig where the sound and 
diseased tissues meet. In the case of fungus attack 
small black spots will often appear on the diseased or 
dead twig. Sometimes twigs are killed by rodents 
eating the bark or by deer brushing it off from the 
underside. If insects have attacked twigs, their pres- 
ence is indicated by borings in the bark or wood. All 
this applies, of course, not only to twigs, but also to 
leaders; in fact, to all the younger shoots of mature 
and immature trees. The youngest twig endings of firs 
may be killed in spring by frost, by a parasitic fungus, 
or by insects. Galls on the twigs or branches are caused 
by insects or by a fungus (Peridermdum) . 

Dead branches and limbs in the otherwise healthy 
crown are always suspicious. The various causes of 
death have been mentioned under " Premature dying 
of the foliage, tops, limbs, branches, or twigs." 

Any alteration of the normal branching system of a 
tree suggests the presence of some injurious agent. 
The mycelium of certain fungi spreads into the twigs 



SYMPTOMS OF DISEASE. 21 

and even into the branches, causing the formation of 
" witches' brooms." These are alterations in the nor- 
mal system of branching peculiar to every species of 
tree, and are due to the stimulation caused by the para- 
site growing in the tissues of the branches or twigs. 
Witches' brooms are very common on wild cherries and 
plums, where they are caused by a fungus. Some 
witches' brooms (on conifers) are produced by mistle- 
toes (p. 56). Occasionally, however, their formation 
is due to excess of nourishment. This is the case 
with the rather rare witches' brooms on yellow pine, 
caused by Peridermium knots, which " girdle " the 
branch and stop the downward flow of the food pre- 
pared in the needles above (p. 39). Other witches' 
brooms are caused by mites or insects. 

Toadstools or conchs (see p. 28 and PL V and others) 
on trunks and limbs indicate the presence of parasitic 
fungi and rot in the wood. Until they develop, no out- 
ward sign of disease may be visible. Diseases of the 
trunk or limbs may affect either the sapwood or the 
heartwood, or both. Disease of the sapwood of conif- 
erous trees is often indicated by a heavy flow of resin 
from the bark. Resin flow on the butt of the tree 
points to disease of the root collar and the roots. In 
cases of this kind we will often find white mycelium 
(see p. 25) under the bark or between the bark scales of 
the butt (see pp. 42 and 53). On the trunk, where it is 
not clearly explained by a wound, it is always more or 
less suspicious. 

It is well to be on the lookout for any abnormal ap- 
pearance of the trunk. Cat faces, burls, thick protrud- 
ing knots, deep knot holes, and abnormal resin flow 



22 FOREST TREE DISEASES. 

are always suspicious, and while the decay which they 
very commonly indicate may not in all cases extend 
very far, it must not be left out of consideration. Decay 
very frequently extends down the trunk from dead 
limbs and dead tops. How far the decay extends 
through the trunk depends very much upon the species 
of tree and the species of fungus inhabiting it. The 
resinous pines suffer least; in spike-topped Douglas 
firs, white firs, and red firs usually one or more upper 
logs are decayed. In judging a tree every slight swell- 
ing and depression on the trunk has to be considered, 
as well as the appearance, color, and quality of the 
bark. This involves, of course, a thorough knowledge 
of normal conditions. 

Heartrot is not a disease in the proper sense of the 
word; the heartwood is dead and thus can not be said 
to be diseased. Heartrots, however, are extremely im- 
portant from an economic point of view, and are 
therefore usually treated as timber diseases. It is often 
very difficult to diagnose typical heartrot from the out- 
side. In very many cases the tree outwardly appears 
to be perfectly healthy, while the heartwood is almost 
completely destroyed. In seemingly sound white fir 
logs it is often possible to diagnose decay from the 
Indian paint fungus by the presence of branch stubs 
which show the characteristic rusty-red color produced 
by this fungus ("rusty knots"; see p. 51). 

In our semiarid mountains, many stools (conchs or 
fruiting bodies, p. 25) of the fungi which cause heart- 
rot are produced during fall, winter, or spring, and 
with exception of the harder, more woodlike forms, 



SYMPTOMS OF DISEASE. 23 

are soon destroyed by insect larvae or by squirrels. 
Careful observation will frequently detect at least some 
remains of these stools. On incense cedar, for instance, 
the soft and juicy fruiting bodies are readily destroyed 
by the larvae of certain insects, many of which then bore 
into the dead outer bark of the tree. These are eagerly 
sought after by woodpeckers, which chop them out of 
the bark. The space formerly occupied by the fruit- 
ing body then appears as a cup-shaped depression, 
which seems to be pierced by innumerable fine shot 
holes, the burrows of the insect larvae. Insect work on 
pines is indicated by pitch tubes on the bark, which 
are characteristic of the attack of Dendroctonus beetles. 
In such cases the bark should be peeled off here and 
there to verify the presence of insect work. 

Longitudinal rows of small holes in the wood are 
caused either by woodpeckers or by the roots of mis- 
tletoes. The latter kind are particularly conspicuous 
in the sapwood under the bark. Woodpeckers very 
frequently bore horizontal rows of holes in the bark, 
which often heal over, leaving, as an outward sign, 
peculiar protruding ridges. 

The weakening of a tree by one injurious agent very 
often opens the road to another, which would not have 
been able to attack the sound tree. Cankers on the 
trunks of white fir, caused by Razoumofskya, are very 
commonly connected with stringy brown rot, caused by 
Echinodontium tinctorum (p. 50). Certain insects 
almost invariably follow injury by fire. Insects and 
parasitic fungi or mistletoe very often work in this way 
for each other and in collaboration. 



,»*' Av<- 



24 FOREST TREE DISEASES. 

All the injurious agencies mentioned can combine. 
The same tree might suffer at the same time from 
needle miners, needle disease, mistletoes, root diseases, 
bark beetles, drought, etc. Different diseases will also 
attack the same tree at different stages of its life. 

FUNGI. 
NATURE AND DEVELOPMENT. 

Most of the diseases of our forest trees are due to 
fungi. A fungus is a very simple plant without green 
pigment, and as such is unable to assimilate carbon 
dioxide. It is unable to live on simple food and to build 
up more complex chemical matter. A fungus lives on 
highly composite matter produced by green plants and 
decomposes it into simple matter, which again becomes 
available for green plants. The fungi share this func- 
tion with the bacteria and animals, and therefore play 
a very important part in nature's economy. A great 
number of fungi live in the soil on dead, decomposing 
vegetable and animal matter; others attack living 
plants, and in so far as they injure or destroy these by 
living on and in their tissues are called parasites. 

Not all wood-destroying fungi can live indiscrimi- 
nately in all trees; some are confined to one species, 
others have a predilection for certain groups of trees. 
They are just as dependent upon certain definite kinds 
of food as are other plants and animals. Few attack 
any trees within their reach. Different fungi not only 
have a distinct predilection for certain species of trees, 



FUNGI. 25 

but also for certain parts of the tree. A leaf or needle 
fungus, for example, will never attack the heartwood 
or the roots of a tree. 

The fungous plant proper consists of extremely deli- 
cate threads (hyphse), mostly invisible to the naked eye, 
unless they appear in masses, for instance, in shape of 
white felts in decayed wood. The hyphse of a fungus 
are called, collectively, mycelium (PI. VIII). The 
hypha? of the parasitic fungi we are mostly concerned 
with live inside the tree, in the tissues of the trunk, roots, 
or leaves. They grow and produce fruiting bodies 
(sporophores). As the name indicates, these are not 
the fungus itself, but what may be termed its " fruit," 
producing " spores." The conch or stool on the trunk 
of a Douglas fir, for example, is not the fungous plant ; 
this lives in the interior of the tree, and the conch is 
nothing but the fruiting body. 

The fruiting bodies are only formed after the fungus 
plant (mycelium) in the host tree has reached a cer- 
tain maturity at the cost of the tissues (cells or cell 
contents) they live in. The fruiting bodies of some 
fungi are formed annually; others are perennial. The 
mycelium of a fungus may be likened to the root system 
of the higher plants, which pervades a given volume 
of soil according to the species and the state of devel- 
opment of the plant. In the same way in which the 
root system of a mature grass plant, for instance, takes 
its raw food and water from an infinitely smaller vol- 
ume of soil than that of a mature yellow pine, the 
mycelium of a needle-inhabiting fungus occupies a 
very much smaller volume of host tissue than that of 



26 FOREST TREE DISEASES. 

a wood-destroying fungus in a large tree. At the 
earliest stage of development the mycelium of a wood- 
destroying fungus, starting, for instance, from a large 
burn in the butt of the tree, lives on a few wood cells ; 
in other words, the volume of decayed wood is still 
very small; in growing the mycelium permeates a 
larger volume of wood, and when it is sufficiently ma- 
ture to produce fruiting bodies it must have drawn its 
substance from a considerable volume of wood, which, 
in doing so, it has reduced to what we call decay. The 
first appearance of a fruiting body on the bole of 
the affected tree, therefore, gives us an indication of 
a certain development of mycelium in the heartwood 
and, consequently, of the extent of decay. Annual 
fruiting bodies grow very fast, and are either de- 
stroyed during summer by insect larvae and squirrels or 
they die off in fall and rot. The mycelium in the 
tree, however, continues to grow by attacking hitherto 
sound wood, and in the next year a new fruiting body 
indicates the progress of the mycelium in the wood and, 
consequently, of the decay. Perennial fruiting bodies 
grow in size from year to year; therefore, their dimen- 
sions will constitute an equally valuable indication as 
to the corresponding extent of the mycelium and the 
decay in the heartwood. Practical knowledge of this 
relation becomes particularly valuable in reconnais- 
sance and in estimating standing timber. 

The extent of decay varies, of course, very much, 
not only with the species of fungus and the species of 
tree, buju also with the development of heartwood and 
its chemical and physical qualities. Evidently there 






% 



FUNGI. 27 

can be no heartrot in trees too young to form heart- 
wood; but even after the differentiation of the wood 
into heartwood and sap wood has begun, the heartwood 
is for a time more or less immune from attack. After 
a number of years, however, the heartwood has changed 
so much in character that it becomes proper food for 
heartwood-destroying fungi. The relative extent of 
decay by E chinodontium tinctorum is far greater in 
slow-growing, suppressed white firs than in thrifty ones, 
in part, perhaps, because the heartwood of thrifty- 
growing trees differs in character from that of sup- 
pressed trees. 

The decay is due to the action of the fungus hyphse 
on the cell-walls of the wood. They use certain com- 
ponents of the cell-walls for food and leave the rest, 
so that the structure of the cell-walls is broken down. 
Wood recently invaded by the hyphse does not yet show 
actual decay ; although it is already under the influence 
of the " advance guard " of the fungus, it appears sound 
or only slightly changed in color or consistency. It is 
only after prolonged action of the mycelium that the 
wood structure actually breaks down. Thus, the wood 
sepajs&tin'g the dry-rot pockets in incense cedar caused 
hj^Polyjyorus amarus (p. 46) looks perfectly sound, 
alplough it must, of course, contain hyphse which con- 
/jjlct the mycelium of one pocket with another ; it has 
jlcst nothing of its strength, while tli(| wood in the 
Ipockets is completely destroyed. In the development 
uof the mycelium of the Indian paint fungus in white 
fir the hyphse advance steadily, not in leaps, as that 
of Polyporvs amarus in incense cedar.yThe part of the 



28 FOREST TREE DISEASES. 

wood covered by these pioneer hyphse, although some- 
what discolored and spongy, often appears sound 
enough to be given full scale. In reality, it has lost a 
good deal of its strength and generally falls to pieces 
in drying after having gone through the mill. Tim- 
ber with this " advance rot " should be classed as cull. 
The classification of white fir by lumbermen as an 
" inferior species " is very largely due to financial 
losses arising from handling logs with advance rot. 

The presence of a fruiting body on a dead or dying 
tree does not necessarily constitute a cause of alarm, as 
many fungi are not only harmless, but absolutely neces- 
sary for the economic equilibrium of nature. The pres- 
ence, however, of any fungus in leaves, needles, or 
fruits (cones) or of any fruiting body on a living tree 
is at least suspicious. 

Young fruiting bodies naturally differ very much in 
aspect from older or dry specimens or ones that may be 
abnormally developed ; in comparing a fungus found in 
the field with descriptions or photographs given in this 
manual, these two points must not be overlooked. 

In nature we find an enormous variety of fruiting 
bodies. These may appear on needles and twigs in the 
form of small, round black spots or black lines and on 
tree trunks, logs, or branches as stools (shelves, conchs, 
toadstools), or crusts. In different ways they all pro- 
duce spores (" seed ") in enormous quantities. 

The spores are invisible to the naked eye, are very 
light, and are carried about by air currents and some- 
times by insects to other trees. Wherever they find 
favorable conditions they germinate and start their 



FUNGI. 29 

destructive activity. Thus a single spore of diminutive 
size may be the cause of complete destruction of a large 
mature tree. 

The spores of fruiting bodies which appear in the 
form of shelves, conchs, or toadstools are usually de- 
veloped on the underside. This underside or lower 
surface is nearly always more or less horizontal, which 
often makes it possible to determine whether a fruit- 
ing body was formed on the living tree or after the tree 
had fallen. In this group of fungi the underside of 
the fruiting body is either porous (PL IV), spiny (PL 
XVII), or gill-bearing (PL III). 

FUNGI WITH FRUITING BODIES IN THE FORM OF STOOLS OR 

CRUSTS. 

POROUS FUNGI. 

In porous fungi the underside is pierced by innumer- 
able holes (pores) which are the openings of tubes. 
These tubes are nearly always perpendicular, and the 
spores are developed on the lining of the walls. The 
pores are sometimes elongated, forming an irregular 
network. Fungi of this group are often injurious to 
cut timber, such as railroad ties (PL II). The fruit- 
ing bodies of the porous fungi are described as shelf, 
bracket, or hoof-shaped, or as crusts, according to their 
form. 

SPINY FUNGI. 

The underside of fruiting bodies of this kind of 
fungus is made up of spines or teeth, on the surface of 



30 FOREST TREE DISEASES. 

which the spores are developed. Examples are the 
fungus causing the stringy brown rot of white fir 
{E chinodontium tinctorum, PI. XVII), which is per- 
haps the greatest enemy of this species ; and the fungus 
Hydnum erinaceus, which causes a destructive rot of 
the heartwood of oak. While the spiny fungi are not 
found on many species of trees, they are very injurious. 

GILL-BEARING FUNGI. 

This group takes its name from the regular blade- 
like gills on the underside of the fruiting bodies, radiat- 
ing from the stalk (mushrooms). The spores are de- 
veloped on the sides of the gills. 

FUNGI WITH FRUITING BODIES NOT IN THE FORM OF STOOLS 

OR CRUSTS. 

LEAF AND TWIG FUNGI. 

The fruiting bodies of leaf and twig fungi present a 
great variety of forms, often, however, they appear as 
black spots or lines. They, too, produce spores, which 
carry the disease to sound organs. 

ATTACK ON VITAL AND NONVITAL PARTS OF THE TREE. 

The fungi which attack forest trees may be di- 
vided roughly into two groups — those which cause 
disease or death of vital parts of a tree and those which 
destroy nonvital parts. 

FUNGI WHICH ATTACK VITAL PARTS OF THE TREE. 

An example of the first group are the needle fungi. 
Partial destruction of the foliage is not always fatal 



FUNGI. 31 

to a tree, but in consequence of the starvation of the 
cambium there is little or no annual growth. Other 
fungi will destroy the roots and the living bark and 
cambium of the butt, and often the tree will die, but 
in the case of trees with a rich flow of resin, such as 
pines, the resin will not allow the fungus to develop in 
the wood of the trunk, which remains sound until it is 
attacked and destroyed by other nonparasitic fungi. 
The timber in such trees can be saved, if disposed of in 
time. Firs, on the other hand, are less effectively pro- 
tected by resin, and the mycelium, entering the trunk, 
causes decay of the dead heartwood. Twig-inhabiting 
fungi often cause distortions. 

FUNGI WHICH ATTACK NONVITAL PARTS OF THE TREE. 

This group includes the economically very important 
wood-destroying fungi. They can not strictly be called 
parasites, since they live in the dead heartwood. They 
rarely endanger the life of the tree. Completely hol- 
low white firs and Douglas firs often appear thrifty. 
However, these fungi often bring about indirectly the 
death of the tree by weakening it mechanically to such 
an extent that it is blown over or broken off in a heavy 
storm. 

The destruction of valuable timber by these fungi 
means ver}^ heavy financial losses, not only in mer- 
chantable timber, but in the ensuing depreciation in 
value of the affected species. Incense cedar, instead of 
ranking as an " inferior " species, would be one of the 
most valuable forest trees of the Sierra Nevada were 
it not for the fact that often as much as 75 or even 



32 



FOREST TEEE DISEASES. 



100 per cent of mature incense cedar is affected with 
dry rot. The same is true, although not always to the 
same extent, of white fir and red fir. 

The fungi of this group are all more or less closely 
related to one another. Their fruiting bodies are usu- 
ally large and conspicuous, and appear in the shape of 
conchs, shelves, toadstools, or crusts (see p. 29). Some 
develop fruiting bodies on the living tree, others after 
the death of their victim, or on both the living and the 
dead tree. 

DISEASES OF FOLIAGE, TWIGS, AND BRANCHES. 



EFFECT. 

Needle and leaf, twig and branch diseases affect the 
prospective value of growing trees — that is, the future 
crop — since they interfere with the production of mer- 
chantable timber; wood-destroying fungi, on the other 
hand, endanger our present capital of timber. The 
diseases of the foliage, twigs, and branches are more 
dangerous to immature than to mature trees. If only 
a few leaves and branches are killed, others replace 
them, or their functions are taken over by those that 
remain. When, however, the damage is considerable, 
the remaining organs are not able to assume the Avhole 
work, and the equilibrium between foliage and root 
system is seriously disturbed. Growth is retarded, and 
the tree may eventually die. If this should happen 
before the tree is ready for the ax, the loss in expected 
timber is complete. Should an old tree die from the 
attack of these fungi, on the other hand, the damage 



DISEASES OF FOLIAGE, ETC. 33 

done, from a commercial viewpoint, consists only in the 
cessation of annual growth. The timber already 
formed remains available, unless destroyed b} 7 second- 
ary, nonparasitic fungi. 

NEEDLE DISEASE OF WHITE AND RED FIR. 

A disease of young white and red fir kills all needles 
except the j^oungest on the ends of the twigs, causing 
them to turn reddish gray, and finally to drop off. The 
green needles which remain on the ends of the twigs 
give the almost naked tree a green outline. The lower 
parts of the tree suffer most. In severe cases the dis- 
ease results in almost complete defoliation. The fruit- 
ing bodies of the fungus Lophodermium nervisequium 
ajDpear in long black streaks following the middle line 
on the underside of the needles. 

TAR-SPOT FUNGUS. 

The fungus Rhytisma is occasionally found on the 
leaves of Oregon maple (broadleaf maple). It takes 
its name from the black, tar-like dots which are evenly 
distributed over round, yellowish, slightly raised spots 
of about the size of a nickel. The black dots contain 
the very small fruiting bodies. If in great numbers, 
these spots seriously interfere with the functions of the 
leaves. 

NEEDLE FUNGUS OF LODGEPOLE PINE. 

The foliage of lodgepole pine, especially in stands 
about the higher meadows of the Sierra Nevada, often 
50977°— 14 3 



34 FOREST TREE DISEASES. 

appears exceedingly thin. Most of the needles' have 
dropped off, and the few that remain are either dying 
or dead. The only green needles stand in a meager 
tuft at the end of the twig. The damage is due to the 
attack of a needle fungus (a species of Hypoderma) , 
the leaves showing broad, transverse zones of light gray 
or yellowish brown, sometimes alternating with zones 
of green. The fruiting bodies appear on both sides of 
the middle nerve in the shape of short, narrow, black 
lines. The disease seems to be quite serious in some 
localities and is likely to do great damage where it 
results in almost complete defoliation of the tree. 

NEEDLE DISEASE OF YELLOW PINE. 

The needles of yellow pine, which normally remain 
on the twigs from 3 to 7 } ears, are often killed down to 
the last one or two years by a fungus (probably a 
species of Lophodermium) , and either drop off, with 
the result that the foliage appears very thin, or else 
remain hanging on the branches for many years, giv- 
ing the tree a " whiskered " appearance. From green 
they turn to yellow and later to silvery gray. The 
increment of the tree is very seriously affected by this 
disease, which does considerable damage. The fruiting 
bodies of the fungus appear in the shape of very small, 
black, irregular spots or short lines. 

STUNTING NEEDLE FUNGUS OF YELLOW AND JEFFREY 

PINES. 

A very destructive needle fungus {Hypoderma) at- 
tacks both yellow and Jeffrey pine, often killing all 



DISEASES OF FOLIAGE, ETC. 35 

needles except the very youngest and weakening even 
these. The needles are mostly short and stunted, or 
characteristically curled. The fruiting bodies appear 
in thin, black lines from one-eighth to one-half inch 
in length. Sometimes the disease appears to attack 
only certain branches; in other cases the entire tree 
is affected. It may also enter the twigs and cripple 
them, causing the formation of " witches' brooms." 

YELLOW AVITCHES' BROOMS OF AVHITE AND RED FIR. 

A bright yellow witches' broom of peculiar shape ap- 
pears on the branches of older red and white fir, due to 
a fungus {Peridermium elatinum), which develops its 
fruiting bodies on the deformed needles. The yellow 
witches' brooms are very conspicuous, standing out 
strongly against the dark green of the sound foliage. 

INCENSE CEDAR RUST. 

This disease is confined to incense cedar of all ages. 
The same fungus (Gymnosporangium hlasdaleanurrb) 
causes two distinct forms of it, both of which may 
appear, together with intermediate forms, on the same 
tree. 

In early spring many of the small sprays of incense 
cedar trees, from sapling to pole size, especially those 
growing in clamp gulches, appear slightly discolored. 
On the under side, or more rarely the upper side, of the 
green, flat, scale-like leaves a number of small, hairy, 
brown to brick-colored tufts or cushions appear. When 
mature, these cushions become gelatinous during the 



36 FOREST TREE DISEASES. 

spring rains and finally unite with neighboring cush- 
ions to form rather conspicuous, slimy, and light 
orange-colored masses, which later dry up to a thin 
film and finally drop off. By this time the sprays have 
turned quite yellow. Later they die. 

This form of the disease must not be confounded 
with the work of a beetle which girdles the twigs, 
causing them suddenly to turn yellowish-white and 
hang down as though broken. Sprays killed by a rust 
never have this appearance and are yellower than those 
killed by the beetle. The small cushions on the under- 
side of the leaves are composed of the winter spores of 
the fungus. These germinate during the warm spring 
rains, and produce a second kind of very small spores. 
The fungus leaves the incense cedar for the time being 
and chooses another host (western service-berry), upon 
the young leaves of which the secondary spores germi- 
nate. After a short time very small, orange-colored, 
cup-shaped fruiting bodies appear on the leaves, and 
the spores produced in these are then again able to 
infect incense cedar. 

Incense cedar witches' brooms, which are very com- 
mon, are also caused by the rust fungus. Only the 
smaller sprays, apparently, are killed by the mycelium. 
If these alone are attacked, no deformation of the 
host tree is noticeable. When the mycelium enters an 
older twig, however, it locally changes the branch- 
ing system. The resulting witches' brooms (p. 21) are 
numerous and conspicuous. The cushions of winter 
spores develop on small sprays at the base of these, and 



DISEASES OF FOLIAGE, ETC. 37 

the sprays usually turn yellow and die. Badly infected 
trees may be seriously injured. Witches' brooms are 
found even on small saplings. 

At a distance the witches' brooms might be taken for 
plants of the incense cedar mistletoe (p. 57). The lat- 
ter, however, always hangs down in thick clusters, 
while the bushy witches' brooms stand more or less 
erect. 

BLUE WITCHES' BROOMS OF SUGAR PINE. 

Sugar pine is comparatively free from diseases of 
the crown. A very peculiar witches' broom, however, 
is found on many trees in the shape of a small ball, con- 
sisting of exceedingly short, brittle twigs and very 
small, brittle, bluish needles. This seldom has a di- 
ameter of more than from 4 to 8 inches, and is gener- 
ally of no economic importance. Several hundred of 
these balls, however, have been found on a sugar pine 
of pole size, showing that under certain circumstances 
a seemingly harmless disease may become injurious. 
The cause of the disease is unknown, but it is evidently 
of parasitic character. 

TIP-DYING OF WHITE AND DOUGLAS FIR. 

White and Douglas fir saplings and poles often have 
dead, yellow, or brown tips hanging from the otherwise 
thrifty branches. This may be the result of an attack 
by a fungus which invades the young, bright-green 
shoots developed in spring, when they are about 1J 



38 FOREST TREE DISEASES. 

inches long. The disease, by killing all the branch tips 
and the leaders, brings about faulty branching and 
spike tops, giving the tree a shrubby appearance and 
sometimes stunting it to such an extent as almost to 
change its entire aspect. The disease also seriously im- 
pairs the natural straight growth of young stuff. 
Similar symptoms may be caused by late frosts or by 
insects. 

BLACK COBWEB FUNGI. 

The fungi Herpotrichia nigra and Neopeckia are 
found only at high elevations with abundant snowfall. 
They are very common on seedlings and saplings of all 
conifers growing in such situations, particularly on 
lodgepole pine, incense cedar, and red and white fir, 
and sometimes cause considerable damage. The black 
mycelium of both fungi lives on the outside of the 
needles. It grows under and on the snow, covering 
the bunches of needles with a brown or black, coarse 
cobweb, and killing them. The spores are formed in 
very small, round, black fruiting bodies, which develop 
on the mycelium. 

PINE GALL FUNGUS. 

Stems and branches of young yellow, Jeffrey, sugar, 
and lodgepole pines often show a peculiar roundish 
swelling, usually from one-half to 4 or more inches 
in diameter and from 1 to 5 inches long. On the trunks 
of lodgepole pine, however, the galls may be much 
larger. The fungi (Periclermivm harknessiu PI. I) 
which causes them belongs to the rusts. The bark of the 



DISEASES OF FOLIAGE, ETC. 39 

swellings comes off in flakes, revealing a bright orange- 
yellow powdery coating, partly covered by a thin white 
film. The same orange-yellow powder consisting of 
spores escapes from small bladder-like pockets with a 
thin white lining, which are conspicuous between the 
bark cracks of the swelling. The wood in these galls is 
excessively developed ; the regular channels in the sap- 
wood through which the water is pumped up beyond the 
galls are disturbed, and the water flow ceases. The liv- 
ing bark is killed and destroyed. As long as the up- 
ward flow of water in the wood of the branch and the 
downward flow of food prepared in the needles are not 
completely stopped, a very rich but temporary develop- 
ment of foliage beyond the gall may result from the 
girdling action of the fungus. Such strikingly full and 
luxuriantly green branches are sometimes very con- 
spicuous on yellow pine, where, however, they may also 
be the result of girdling by mistletoe. (See Mistletoes, 
p. 56.) In time the flow of water and prepared food 
is cut off, and the branch and needles beyond the 
gall die. This disease constitutes a serious menace to 
seedlings and smaller saplings of yellow and Jeffrey 
pine, frequently killing them in groups. When it 
attacks the leader it seriously interferes with the 
normal growth of the young tree. Lodgepole pine, 
especially in the northern California forests, suffers 
severely, many seedlings being killed, and trees up to 
pole age completely stunted, and sometimes killed. The 
very similar galls on Monterey pine are also caused by 
a PeridermAum (probably P. cerebrum) . 



40 FOREST TREE DISEASES. 

DISEASES OF ROOTS, TRUNKS, AND LIMBS. 

EFFECT. 

Typical diseases of the stem (heartrots) invariably 
do a great deal of damage by destroying merchantable 
timber, often, however, without impairing the health 
and growth of the tree except in weakening it mechanic- 
ally. Different fungi act in different ways on the 
wood they inhabit ; in other words, every fungus causes 
a more or less characteristic decay by which, in many 
cases, we can determine the kind of fungus in the ab- 
sence of fruiting bodies (sporophores). Entering the 
tree through a wound or some other opening in the 
bark, the mycelium of the fungus grows in the dead 
heartwood. As a rule the living sapwood is untouched. 
The inability of most of the fungi of this class to in- 
vade living tissue explains why they are only found on 
older trees and not on younger ones, which contain no 
or very little heartwood. The age at which the trees 
of a given species may become infected varies and is 
closely connected with the age at which the species 
forms heartwood ; it varies also with the species of the 
attacking fungus. In general, diseases of the trunk 
are rare in sugar pine, more frequent in yellow and 
Jeffrey pine, common in Douglas fir and red fir, and 
very common in incense cedar and white fir. 

The fungi which cause root diseases, on the other 
hand, are able to attack living tissue, at least when 
offered entrance by a wound caused by rodents, plow- 
ing, etc. They invade and kill the living bark, the 



DISEASES OF ROOTS, ETC. 41 



cambium, and the sapwood. As long as connecting 
parts of these remain intact, the tree will not die, 
though it may be greatly weakened. With the progress 
of the fungus, however, the remaining sound sapwood 
can no longer supply the crown and foliage with water. 
The weakened foliage stops respiration and assimila- 
tion; bark and cambium are not sufficiently nourished, 
and the root system is starved. The final result is 
death of the tree. The fungi of this group are not, as 
a rule, confined to trees of any particular age. 

Root diseases can not well be separated from diseases 
of the stem, since the fungi which cause them, after 
living for a while off the roots, may, except in very 
resinous trees, invade the trunk. Root diseases of forest 
trees, which, with few exceptions, are at present not 
very important in District 5, are caused by fungi with 
porous or gill-bearing fruiting bodies, which grow on 
the roots and on the collar of the tree. Where they do 
appear, however, they are extremely injurious. They 
spread not only by dissemination of spores, but also 
from infected roots to sound ones of neighboring trees. 
White mycelium found at the collar of a living or 
recently killed tree, between the bark and wood or 
between the bark scales, usually indicates the presence 
of a fungus of this class. Not always does the fungus 
enter the heartwood. In the pines resin prevents the 
mycelium from entering the wood of the trunk. In 
spruce and fir, however, the trunk is invaded and de- 
stroyed. Resin flow on the lower part of the trunk 
often indicates diseases of this kind. 



42 FOREST TREE DISEASES. 

ROOT FOMES. 

This fungus (Fomes annosus — pronounced fomeez) 
is considered in Europe one of the most dangerous 
forest fungi, and is also destructive in the eastern 
United States. Although at present apparently some- 
what rare in California, it may prove to be more preva- 
lent. It attacks almost all conifers of all ages and 
some broadleaf trees. The infection starts in the roots 
and spreads upward, destroying bark, cambium, and 
sapwood and causing the sudden death of the tree. 
The heartwood first appears streaky (bluish) and later 
shows the very characteristic red rot, with small, elon- 
gated, perpendicular white pits, often with a black cen- 
ter (see Trametes pini) . Between the bark scales a very 
fine mycelium appears. In resinous trees the rot is con - 
fined to the butt, but in less resinous ones, such as firs, 
it reaches far up the trunk. The disease spreads not 
only by spores, but also from diseased roots to the sound 
ones of neighboring trees. Whole groups of trees can 
thus die within a very short time (see, however, Armil- 
laria mellea). In this connection it should be remem- 
bered that the sudden dying of groups of trees may 
also be due to attacks by barkbeetles. 1 The perennial 
fruiting bodies of the fungus are more or less crust 
shaped, and porous, and usually grow on the roots, but 
sometimes on the collar of the tree, though generally 
below the surface of the soil. They are tan colored, 
with a white underside and margin. 

1 See publications of the Bureau of Entomology. 



DISEASES OF ROOTS, ETC. 43 

RING SCALE FUNGUS. 

The ring scale fungus (Trametes pi?vi — pronounced 
trameeteez) causes one of the most destructive diseases 
of living mature and overmature conifers. Though the 
perennial fruiting bodies reach a great age — 50 years or 
even more — they are seldom very large, and vary in 
shape according to the host they grow upon. (Pis. IV 
and V.) As a rule they are irregular, hoof-shaped, the 
upper side grayish black, rough, dull, often cracked, 
with concentric furrows parallel to the rather conspicu- 
ous narrow, velvety, light brown margin. The under- 
side is light grayish brown. The pores are very large 
and irregular, varying from relatively small, angular 
ones near the margin to long, sinuous holes forming a 
maze with irregular meshes. The substance of the 
fruiting body is rusty brown in color, and cuts like 
cork. On the pines the fruiting bodies grow out 
through branch scars, and, as a rule, only one or a very 
few of larger size are developed. On white and red 
fir they are generally smaller. On Douglas, white, and 
red fir they often form directly on the bark, usually in 
large numbers. Because of their inconspicuous coloring 
they are easily overlooked. The mycelium spreads rap- 
idly up and down the tree. A cross section of the heart- 
wood shows that certain annual rings are more affected 
by the fungus than the others, hence the name " ring 
scale " (PI. VI), and also that the action of the fungus 
is confined almost entirely to the soft springwood of the 
annual ring, though the color of the hard summerwood 



44 FOREST TREE DISEASES. 

is usually somewhat darker than normal. Split heart- 
wood shows numerous perpendicular white spots or hol- 
low pits, lacking, however, the black centers of those in 
wood destroyed by root fomes. (PI. VI.) In species 
which do not contain much resin the decay may attack 
the sapwood also. 

The fungus gains entrance through knots and wounds, 
and grows in the tree for some time before the fruiting 
bodies develop. To destroy these does not destroy the 
fungus itself, and new fruiting bodies are soon formed 
in place of old ones. Trees infected with ring scale 
fungus should not be tolerated in the forest. 

CHALKY QUININE FUNGUS. 

The chalky quinine fungus (Fomes lands, Pis. VII 
and VIII), forms, together with Trametes pini and 
Armillaria mellea, the onlv serious menace to su^ar 
pine, on which it is most often found. It may, how- 
ever, attack Jeffrey, yellow, and lodgepole pine, Doug- 
las fir, and other conifers. The fungus causes a red 
heartrot, with felts of white mycelium resembling 
somewhat the decay produced by the sulphur fungus. 
On sugar pine the fruiting bodies are generally very 
large, round, and hoof-shaped, with a rough, white 
chalky surface, which becomes slightly yellow or light 
brownish with age. The substance of the perennial 
fruiting body is white, soft and mushy when fresh, 
chalky and friable when dry, and extremely bitter to 
the taste. When rubbed, the surface stains the fingers 



DISEASES OF ROOTS, ETC. 45 

white like chalk. The pores on the underside may wear 
off with age. The fruiting bodies often grow on large 
open wounds, forming large irregular, perpendicular 
rows. Two or more fruiting bodies may appear on the 
same tree at different heights. Altogether the fruiting 
bodies are not common. 

SULPHUR FUNGUS. 

The sulphur fungus (Polyporus sulphureus, PI. IX) 
often attacks living and dead mature and overmature 
oaks, chinquapin, and red fir, but is found also on 
Douglas and white fir, and yellow and Jeffrey pine. It 
is very common and exceedingly destructive. The an- 
nual fruiting bodies appear in clusters of large, rather 
flat, yellow shelves. The upper side of the fruiting 
body is smooth and bright yellow, sometimes light brick 
color. The smooth underside is brilliant sulphur yel- 
low, with small pores. The cheesy, juicy interior is yel- 
low. During summer and fall the fruiting bodies dry 
up, and turn either a dirty yellow, or more often a 
chalky white, and become at the same time brittle. 
They can easily be distinguished from those of Fomes 
laricis, however, by their flat-shaped growth in clusters, 
and absence of bitter taste. The fungus causes a red 
heartrot, with very broad and thick white felts of 
mycelium (PL X), often forming a white star on a 
cross section in the center of limbs and younger trees. 
The sulphur fungus is the most destructive enemy of 
red fir. 



46 FOREST TREE DISEASES. 

INCENSE CEDAR DRY-ROT. 

The dry-rot of incense cedar (called in the East 
" peckiness " or " pin-rot " (Pis. XI and XII), caused 
by the fungus Polyporus amarus, is one of the most 
characteristic tree diseases. The rot consists of brown, 
oblongated pockets, from one-half inch to several feet 
long, filled with a brown, charcoal-like mass, and sepa- 
rated from each other by apparently sound wood (PI. 
XII). The fungus evidently enters through wounds 
or knots, destroys the heartwood, but rarely attacks the 
sapwood. The annual fruiting bodies (PL XI) are at 
first extremely soft and mushy, and later become cheesy 
and somewhat tough. Originally knob-shaped, they 
soon become bracket-shaped, with rounded tops. Fully 
developed fruiting bodies resemble a bell cut lengthwise 
in half. When young they are smooth and tan-colored 
on top, with the underside a bright sulphur yellow, 
becoming brown with age. They issue from knot holes, 
and develop in summer and fall, occasionally after the 
death of the tree. Being fleshy, they are devoured by 
squirrels and insects, and the place they once occupied 
can easily be recognized by the shot-hole effect of the 
larvse holes in the cup-like depression of the outer bark 
hollowed out by woodpeckers (p. 23). Seldom is more 
than one fruiting body found on a living tree at one 
time. Trees less than 2 feet in diameter are generally 
free from the disease unless they are badly suppressed. 
The lower and middle parts are the most affected. 



DISEASES OF ROOTS, ETC. 47 

POLYPORUS SCHWEINITZII. 

Polyposis schweinitzii (PL XIII) is one of the most 
serious enemies of Douglas fir, and also occurs on cer- 
tain pines and on white fir. It continues to live and 
fruit long after killing its host, and rapidly destroys 
the economic value of the timber. The disease gen- 
erally appears on the roots and lower parts of ma- 
ture trees and spreads upward. The decayed wood is 
reddish brown, with very thin, resinous crusts of my- 
celium. Later it becomes friable, and is easily crushed 
between the fingers to a yellow powder. The presence 
of the disease is often disclosed by resin flow on the 
bark at the base of the tree. The annual fruiting 
bodies, which usually appear on old wounds at the base 
of a tree, a little above the ground, or on the soil coming 
from dead tree roots, have a characteristic short, thick 
stalk, are rather large, reddish to dark rusty brown in 
color, with a yellow margin, cheesy when young, and 
soft and corky when dry. The porous underside of 
fresh fruiting bodies is dirty green, and turns deep red 
brown when bruised. The old dry fruiting bodies from 
dead tree roots closely resemble old cow dung, 

RED-BELT FOMES. 

Red-belt fomes {Fomes pinicola, PL XIV) is the 
commonest timber-destroying pore fungus in Califor- 
nia, attacking all the important conifers, except incense 
cedar, juniper, redwood, and bigtree. The perennial 



48 FOREST TEEE DISEASES. 

fruiting bodies are large, blackish on the upper side, 
creamy white on the underside, and usually have a 
broad reddish to chestnut-colored, shiny belt above 
the light margin. On standing trees they are usu- 
ally hoof-shaped. The underside is more or less 
horizontal, smooth, with very small pores, and the 
margin rounded. They vary considerably in shape, 
however, according to where they appear. On the 
underside of logs they may form rounded burls or 
knobs, while on the upper side they occasionally ap- 
pear in the form of short-stalked, broad toadstools. 
The substance of the fruiting bodies, which shows dis- 
tinct layers, is tough, stringy, later woody, and of a 
very light yellow brown or isabel color. Drops of a 
clear liquid often hang from the white underside of 
the fruiting body. The fungus produces a very char- 
acteristic red rot in the heartwood, with broad, white 
felts of mycelium. It is exceedingly destructive to 
fallen timber, and may cause damage to living trees as 
well. On the other hand, it acts as a scavenger on 
waste logs, which are transformed within a compara- 
tively short time into a punky mass. This punky 
wood, however, presents a serious fire menace. A sin- 
gle spark will ; et it to smouldering for days or even 
weeks until a sirong wind fans it into a blaze. 

POLYPORTJS DRYOPHILUS. 

Polyporus dryvjihilus is very common on living oaks. 
The annual fruiting bodies are conspicuous, and either 
grow on the side of the stem or limb, when they are 
hoof -shaped, or else hang from the underside of the 



DISEASES OF ROOTS, ETC. 49 

limb, when their shape is that of a broad bell. The en- 
tire fruiting body is light tan color, though the under- 
side is slightly lighter than the upper. The latter is 
smooth and distinctly velvety to the touch, especially 
toward the margin. The pores of the underside are 
rather small. The substance of the fruiting body va- 
ries in color from tan to brown. The fungus causes a 
destructive heart-rot, which is characterized by coarse, 
dark-brown, and yellowish-white fibers. 

FALSE TINDER FUNGUS. 

The false tinder fungus (Fomes igniarius, PI. XV) 
is confined to deciduous trees, and is especially common 
on willows, cotton Wood, and quaking aspens. It causes 
a white heart-rot which sometimes extends into the 
sapwood. If only the heartwood is destroyed, the tree 
may live for many years, until it is finally broken off 
in a storm or heavy snowfall. When the living sap- 
wood becomes diseased, however, the damage is more 
serious. While the perennial fruiting bodies do not 
grow in groups, a number may appear on the same tree, 
issuing from branch scars. They are hard and usually 
hoof-shaped. In size they vary a good deal, but are 
rarely very large. When young the upper side is vel- 
vety and brown, and when old, dull brown to almost 
black, concentrically furrowed and cracked. The mar 
gin is velvety and of a lighter rust-brown. The under- 
side is a grayish rust -brown to cinnamon, with small 
pores. On the smooth, light bark of the host tree the 
dark fruiting bodies stand out very conspicuously. The 

50977°— 14 4 



50 FOREST TREE DISEASES. 

substance shows distinct annual layers, and the age of 
a fruiting body can with a certain degree of accuracy 
be determined by cutting it lengthwise and counting 
these. 

WHITE TOUCH FUNGUS. 

The white pouch fungus (Polyporus volvatus), which 
causes a slow- working, rather superficial gray rot, is not 
considered parasitic; it does not endanger living trees, 
but it is very common, and a short description of it will, 
therefore, be given here. The annual fruiting bodies 
appear on most conifers, with the exception of juniper, 
redwood, and bigtree, very soon after the death of the 
tree, and sometimes on dead parts of a living tree. 
They are rather small, light yellow -brown when young, 
white with age, hoof-shaped, and soft corky to hard. 
The entire surface is very smooth. The underside, 
with its tiny spores, is hidden by a thick, leathery skin, 
which forms a pouch. The pink spores escape through 
a small hole in this skin. 

INDIAN PAINT FUNGUS. 

The stringy brown rot of white fir, common through- 
out California, is caused by the Indian paint fungus 
{E chinodontium tinctorum, -Pis. XVI, XVII, and 
XVIII), a very destructive organism, with a large, 
black, hoof -shaped, perennial fruiting body. The spines 
or teeth on the underside of the latter are large and 
hard and point downward. The interior is a vivid rust- 
red, and was used by Indians for the preparation of war 
paint. The fruiting bodies grow on the trunk some dis- 



DISEASES OF ROOTS, ETC. 51 

tance up, and from four to six or more may appear at 
different points on the same tree. They never grow out 
through the bark, but invariably issue from pin knots 
or branch stubs. The mycelium from which the fruit- 
ing bodies spring can only get to the exterior of the 
tree by way of branch stubs bridging from the heart- 
wood through the sapwood to the outside. In doing so, 
it decomposes the wood of the stubs, which then, in 
most cases, show streaks of the same rusty color that 
characterizes the inside of the fruiting bodies. These 
" rusty knots " are an infallible sign of decay from the 
action of the Indian paint fungus in the heartwood. 
In scaling seemingly sound white fir logs, careful atten- 
tion should be paid to pin knots and branch stubs. 
Sound stubs are hard and brittle and break off easily 
when hit with the U. S. marking hammer or a similar 
instrument. Unless the log ends show decay, about 
3 to 4 linear feet in both directions from the rusty 
knot should be allowed for cull. The rusty red 
color appears also in streaks in the stringy reddish- 
brown rot of the heartwood, which usually leaves but 
a thin shell of sound sapwood to support the tree. The 
stringy brown-rot represents one of the last stages of 
decay. In the first stages the timber appears practi- 
cally sound to the casual observer; a closer investiga- 
tion, however, will show that the wood is more or less 
discolored and spongy. Length sections reveal small 
light-brown spots. This timber, which has only re- 
cently been invaded by the mycelium, causes serious 
trouble in so far as it will fall to pieces in drying after 
going through the mill (see "advance rot," p. 28). 



52 FOREST TREE DISEASES. 

The advance rot extends about 2 to 6 linear feet beyond 
the unmistakably decayed timber; in scaling, it should 
be treated as cull. Besides white fir, the fungus may 
also attack Douglas fir, and occasionally red fir. It is 
often connected with cankers caused by Razowmofskya 
occiderdalis (p. 58). 

HYDNUM ERINACEUS. 

This fungus is sometimes found on oaks. The large, 
head-shaped, annual fruiting bodies are white, very 
fleshy and juicy when fresh, but later dry up to small 
brown or blackish masses. They are often destroyed by 
insects. Soft, white spines or teeth cover almost the 
entire fruiting body. In the course of the disease the 
heartwood of the tree becomes lighter in color, finally 
appearing almost white, and is rapidly and completely 
destroyed. The stems of oaks affected with this rot 
often consist of but a hollow shell of sapwood. 

HONEY FUNGUS. 

The honey fungus {Armillaria mellea, Pis. XIX and 
XX) is one of the most destructive root fungi of oaks 
and orchard trees (oranges, apricots). In our forests 
it does not appear to be very common, but it is likely 
to spread. It may attack coniferous trees (sugar pine, 
white fir) of all ages, often spreading through dis- 
eased roots to roots of sound neighboring trees, which 
it kills in a short time. The butt of affected conifer- 
ous trees often shows a heavy outflow of resin. Con- 



DISEASES OF ROOTS, ETC. 53 

spicuous tough felts of white mycelium under the bark 
distinguish this fungus from the root fomes (Fomes 
annosus) with its very thin mycelium. Another charac- 
teristic of the honey fungus consists in the black-brown 
round or flattened strands, " shoe strings," which are 
found under the bark or in the soil near the affected 
tree. The parasite is, in fact, sometimes called shoe- 
string fungus. The annual fruiting bodies are honey- 
colored mushrooms with gills (PL XIX) y the stalks 
bearing a thin yellowish ring. They grow in great 
numbers on stumps, bark, or on the ground near the 
base of living or dead trees. 

SCALY LENTINUS. 

Although it is not certain that the scaly lentinus 
(Lentinus lepideus) actually attacks living trees, there 
are indications that it does so. It is certainly very de- 
structive to dead timber. The big white annual fruit- 
ing bodies are often found in large clusters on the butts 
of Jeffrey, yellow, and lodgepole pine. Occasionally, 
however, they grow on the dead roots of living trees 
and also high up on the trunk. The underside of the 
fruiting body has no pores, but is provided with wide 
white gills standing on edge and radiating from a cen- 
tral stalk which is tough and fleshy. The fruiting 
bodies resemble irregularly shaped white mushrooms, 
the upper side of which is at first covered with broad 
yellowish, and later, grayish-brown scales radiating 
from the center to the margin. 



54 FOREST TREE DISEASES. 

MISTLETOE. 

Our forests have, perhaps, no more widely distributed 
parasitic enemies than the mistletoes. Two kinds of 
mistletoes grow on forest trees; one belonging to the 
genus Phoradendron, an example of which is the ordi- 
nary Christmas mistletoe, the other belonging to the 
genus Razoumofskya (Arceuthobium) , and confined to 
coniferous trees. Phoradendron is the larger of the 
two and may have leaves, as on oak, or be leafless, as 
on incense cedar. Its berries are round, white or pink, 
and contain a seed imbedded in a thick, extremely sticky 
glue. The seeds are carried by birds from one tree to 
another, adhere to the bark, and germinate. The 
Phoradendrons are light-seeking, and therefore grow 
high up in the tree (PL XXI). Razoumofskya (PI. 
XXII) is smaller. The thin and brittle stems stand 
out from the branch they grow on like a small yellow- 
ish brush. The oval berries hang on erect stems, and 
are light green in color. In ripening they develop a 
considerable inside pressure, which increases until the 
slightest disturbance is enough to make them explode 
and eject the seed with some force. These are scattered 
about at random, and many perish for lack of food; 
others stick to the bark of young branches and twigs 
and germinate. The Razoumofskya species are more 
tolerant of shade than the Phoradendrons. 

Mistletoe seeds of both groups can germinate under 
normal conditions almost anywhere, but they can pene- 
trate only the young, thin bark of those hosts to which 
they are adapted. For example, Razoumofskya seeds 



MISTLETOE. 55 

(embryos) thrown from a Jeffrey pine onto a twig 
of an oak standing beneath it can germinate, but can 
not penetrate the bark and enter the living tissue. The 
same seed landing on a young Jeffrey pine twig, how- 
ever, develops a small rootlet, which perforates the 
bark. From this rootlet are developed other roots (cor- 
tical roots) running up and down in the bark of the 
twig, and from these again so-called sinkers are 
started — that is, roots growing straight down to the 
wood. In the meantime, the mistletoe plant develops 
on the outside of the twig at the cost of the host tree. 

The damage the mistletoes of both groups cause to 
their host consists less in depreciation of timber than 
in the attack on the vital organs of the host. They 
belong to the higher plants which are characterized by 
roots, stems, green foliage, and flowers. Parasitic life 
has robbed the mistletoes of their independence. The}^ 
are unable to take raw food from the soil; their root 
system is much reduced and has adapted itself to the 
function of tapping the tissues of their hosts. The 
foliage of the Razoumofskyas is reduced to small scales 
and they contain veiy little green pigment (se p. 9) 
with which to assimilate carbon dioxide from the air. 
They depend, therefore, upon their host not only for 
water, but also for the greater part of elaborated food. 
The Phoradendrons, on the other hand, generally 
possess green leaves, or, at least, green stems. They 
elaborate their own food and normally draw only water 
and raw food from the host. 

The effect of the mistletoe on its host is chiefly that 
of a parasite tapping the saps and girdling the branch 



56 FOREST TREE DISEASES. 

it grows on. The irritation of the cambium by the 
roots of the mistletoe results in a considerable swelling 
of the branch at the point of attack. The wood of such 
swellings is very characteristically marked by longitu- 
dinal rows of small holes made by the sinkers. The 
holes caused by the sinkers of Phoradendron are par- 
ticularly conspicuous. 

Mistletoes do not often kill outright. Girdling by 
Razoumofskya can even stimulate for quite a time the 
growth of the branches and leaves above the point of 
attack. This luxuriant growth, however, is of little 
benefit to the tree. The food prepared in the excess 
foliage above the mistletoe serves to nourish the mistle- 
toe plant, and barely sufficient food is allowed to go 
below to the roots to keep them from starving. In 
many cases the attack ends in the death of the branch 
or limb, and when many limbs are affected in the death 
of the tree. Razoumofskya very often causes a forma- 
tion of witches' brooms (p. 21). Large formations of 
this kind, often resembling richly branched, low- 
hanging limbs, with profuse foliage, are very conspicu- 
ous on sugar pine, yellow pine (PI. XXIII), and Jef- 
frey pine, and common on lodgepole pine (PI. XXIV) 
and Douglas fir. Phoradendron sometimes lives for 
a great many years and then causes swellings and 
deformations, for instance, on trunks of incense cedar, 
where the parasite has been known to live for more 
than 220 years. As the rather brittle mistletoe shrubs 
break off easily, rarely lasting more than 10 years, 
new shrubs are formed from buds breaking through 
the bark of the host, as long as the bark is not too 






MISTLETOE. 57 

thick. In cases where incense cedar mistletoe, for in- 
stance, has grown to a high age with its host tree, the 
bark of the latter becomes so thick that it can not 
be pierced by the young mistletoe sprouts. The mistle- 
toe then lives without green parts, consisting only of 
cortical roots and sinkers, and depending altogether for 
all food on its host. In this state it acts very much like 
a fungus, which also is unable to elaborate its own 
food and has to rely upon other plants (see p. 24). 

Phoradendron rarely attacks young trees. Razou- 
mofskya, on the other hand, very often does consid- 
erable damage to young yellow, Jeifrey, and lodgepole 
pine. If the stem or leader is infected, the young tree 
is killed in the course of time, or at least prevented from 
developing a straight, clean bole. Different species of 
Phoradendron and Razoumofskya are confined to cer- 
tain hosts. Phoradendron juniperinum libocedri, for 
example, grows on incense cedar; Phoradendron juni- 
perinum on junipers; Phorandendron bolleanum on 
white fir and juniper; Phoradendron flavescens on oak 
and other broadleaf trees; Razoumofskya campylo- 
poda on sugar, yellow, and Jeffrey pine ; Razoumofskya 
amevicana on lodgepole pine ; Razoumofskya douglasii 
on Douglas fir; and Razoumofskya occidentalis on 
white fir. 

Our white fir is the host of both a Phoradendron and 
a Razoumofskya. The light-seeking Phoradendron 
bolleanum lives exclusively in the very top of the older 
trees, chiefly in the leader, and there develops the con- 
spicuous tufts of green foliage, which even at a great 
distance reveal the presence of the mistletoe. It finally 
kills the leader, which is replaced by a secondary leader, 



58 FOREST TREE DISEASES. 

and this, too, is often killed. This " top " mistletoe is 
responsible for by far the greater number of spike tops 
in white fir, though these are caused also by lightning 
and the Tussock moth. Razoumofskya occidentalism 
which inhabits white fir of all ages, grows lower down 
on twigs and branches and is also often found on limbs 
and the trunk. As it can not penetrate old bark, the 
infection must in the latter case have taken place when 
the tree was young. This shows that the tree can live 
for a long time after infection. The effect on the 
trunk is the development of huge barrel-shaped swell- 
ings, which later break and present a large open wound 
or canker. Besides rendering this part of the tree 
wholly unmerchantable, the swelling, made up of un- 
healthy and abnormal tissue, weakens the tree very con- 
siderably, while the open wound offers an easy entrance 
to germinating spores of Echinodontium tinctomm, the 
cause of the reddish-brown, stringy heartrot. White 
fir snags, broken off in a storm either just below or 
above the canker or in the swelling itself, are extremely 
common. Almost all trees with canker are completely 
worthless from decay. All white fir with this mistle- 
toe should be cut and utilized as soon as possible. 

CONTROL OF DISEASE. 

It is impossible to grow sound, thrifty young trees 
for future stands if conditions in the forest are such 
that there is constant danger from insects and disease. 
Every diseased or abnormal tree (leaning, forked, etc.) 
in the forest, as well as every snag, in other words, 
every individual that can not finally produce the great- 






CONTKOL OF DISEASE. 59 

est amount of high-grade merchantable timber, acts as 
a parasite on the whole community ; it takes space, light, 
and food from the sound trees and places them in con- 
stant danger from infection, attack by insects, and fire. 
The forest is a community of living trees, which 
breathe, assimilate food, grow, adapt themselves to sur- 
rounding conditions, and struggle for life, and which 
are subject to diseases and injuries from which they 
may succumb if not helped in time, exactly like any 
other plant and every animal. The forester in charge 
of these living beings must endeavor to eliminate any 
danger to their health, to prevent their injury, and to 
establish sound conditions for their growth. These are 
the objects of forest hygiene, upon the application of 
which the welfare of the community depends. 

The first step in any hygienic work is close observa- 
tion. Unless the field man keeps a sharp lookout for 
signs of disease or abnormality in individual trees, he 
will in all likelihood fail to see an unhealthy condition 
in the stand and so lose the opportunity to remedy it. 
Under " Symptoms of disease," page 18, a number of 
hints are given on how to recognize any trouble. 

There are a number of injurious factors which we 
can not control, such as lightning, drought, and floods. 
Fires which can be controlled have more to do with 
decay of forest trees than is commonly supposed, since 
fire scars very often offer an easy entrance to wood- 
destroying fungi and to wood borers. 

It is manifest that expensive measures, such as treat- 
ment of wounds, pruning, spraying, and the construc- 
tion of isolation ditches, can not be applied in our enor- 



60 FOREST TREE DISEASES. 

mous forests as in the smaller and more valuable Euro- 
pean forests, or in orchards and parks. Methods must 
be adapted to existing conditions. 

Very rarely will it be possible to save a tree or a 
stand which has once been attacked by one of its more 
dangerous enemies. A tree infected by a heart-rot fun- 
gus or by a large colony of Dendroctonus beetles is 
lost. We can not save it. We can not even always save 
all of its timber; part of it may already be destroyed 
or at least injured. This leads to our first rule: Save 
the merchantable timber of a tree as long as the amount 
to be saved justifies it. This simply means closer 
utilization of our timber supply. 

The second rule in dealing with disease is to prevent 
the infection and infestation of sound stuff by getting 
rid of all diseased and insect-infested living or dying 
trees. This means sanitation of our forests. Insects, 
fungi, and mistletoe, however, are so widely and uni- 
formly scattered throughout our forests, and have such 
a firm hold, that without improved methods of forest 
management it will take long and persistent work to 
control them. 

There is a fundamental difference between attacks by 
insects and by parasitic plants (fungi and mistletoes). 
While insects are always present in the forest, it is 
only at considerable intervals that they do widespread 
harm in any given locality. A destructive species, 
however, may multiply enormously and kill a large 
number of trees in a short time. Under natural condi- 
tions it may continue to increase in number for years 
until it is again reduced by some natural agency to a 



CONTROL OF DISEASE. 61 

scattered and harmless condition. Parasitic fungi and 
mistletoes, on the other hand, develop rather slowly, 
and spread their activity over long periods. Sudden 
outbreaks of disease, regular epidemics, are rare. The 
only sudden danger might come from leaf, twig, bark, 
and root diseases. 

Prevention is the basis of control of parasitic fungi 
and mistletoe. The greatest difficulty lies in the fact 
that the spores of injurious fungi are found everywhere, 
being carried long distances by air currents. It follows 
that fruiting bodies of parasitic tree fungi should be 
destroyed by fire, if possible, wherever found. A young 
tree whose stem is affected with mistletoe can never pro- 
duce a straight, sound trunk. It is therefore better to 
destroy it, in order to make room for sound reproduc- 
tion. A mistletoe-infested branch should be cut off 
some distance from where the mistletoe appears, since 
its roots may spread rather far toward the trunk in the 
living bark. Trees with infected steins or trunks can 
not be saved. 

The practice of cutting mistletoe-infected trees out- 
side of timber-sale areas would, of course, be practicable 
only along roads and trails. More systematic and valu- 
able work can be done by every ranger around his 
regular station. Just as the neatness and cleanliness of 
an office would always speak for the quality of the 
ranger who is in charge of it, so the clean and healthy 
condition of the forest about the ranger station should 
testify to the ranger's credit. Ranger sales and free 
use are means by which the ranger can very materially 
help in establishing healthy conditions on the forest 



62 FOREST TREE DISEASES. 

at large. Wherever possible all undesirable timber 
should be used first for these purposes. A tree affected 
with needle disease, mistletoe, or even bark beetles will 
usually answer just as well as a perfectly sound one. 
Incense cedar with dry-rot not too far advanced makes 
as good posts as sound cedar. A tree once affected by 
any serious parasite, if left long in the forest, deteri- 
orates very rapidly, and unless the merchantable tim- 
ber it contains is utilized in time it will go to total 
waste. 

The surroundings of nurseries and planting areas 
should also present as healthy conditions as possible. 
We can not expect to raise sound, thrifty reproduction 
in an insanitary environment. 

The difficulties in the way of bettering hygienic con- 
ditions and establishing sanitation in our forests on a 
large scale are, of course, very great. Although it is 
comparatively simple, for instance, to trace damage to 
smelter fumes or smoke, it is generally a hard task to 
stop the trouble. Systematic elimination of the com- 
mon fungi or mistletoes will take many years. The 
method which gives the best results is illustrated by a 
stipulation inserted in the Forest Service timber-sale 
contracts. This requires the purchaser to cut all trees 
marked upon the cutting area, whether merchantable 
or apparently unmerchantable. Trees must be opened 
up sufficiently to satisfy the forest officer in charge of 
their condition, and any logs in such trees which, in 
his judgment, are merchantable must be removed from 
the woods, scaled, and paid for. This enables the 
Forest Service to get rid of all undesirable stuff and to 



CONTROL OF DISEASE. 63 

leave only sound seed trees and sound reproduction in 
healthy surroundings. It also makes possible utiliza- 
tion of merchantable timber left in undesirable trees, 
which would otherwise go to waste. 

One other point should be borne in mind by every 
forest officer who has to do with marking timber. 
Seed trees left for reproduction should be sound and 
not too old. Neither in animal nor in plant life can 
healthy, thrifty offspring be expected from diseased, 
weak, or aged parents. The future of the forest de- 
pends very largely upon the right choice of seed trees. 



Forest Tree Diseases, Forest Service, U, S. Dept. of Agriculture. 



Plate I. 




Fungus Gall on Yellow Pine Caused by Peridermium harknessii 

(Photograph by Dr. Herman von Sehrenk.) 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate II. 




Forest Tree Diseases, Forest Service, U. S. Dept of Agriculture. 



Plate III. 




Gill-Bearing Fungus (Pleurotus). 
(Photograph by Dr. G. G. Hedgcock.) 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate IV. 




Trametes pini Fruiting Bodies on Shortleaf Pine. (Compare with 

Plate V.) 

(Photograph by Dr. <;.<;. Hedgcock.) 



Forest Tiee Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate V. 




Trametes pini Fruiting Bodies on Lodgepole Pine. (Notice, in 
Comparison with Plate IV, Variation in Form with Host 
Tree.) 

(Photograph by Dr. G. G. Hedgeook.) 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate VI. 




Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate VII. 




Chalky Quinine Fungus (Fomes laricis) Fruiting Body on Douglas 

Fir. 
(Photograph by Dr. G. G. Hedgcoek.) 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate VIII 




Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate IX. 







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Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate X. 




Sulphur Fungus Rot in the Heartwood of Oak. 
(Photograph by Dr. Herman von Schrenk.) 






Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. PLATE XI. 




Fully Developed Fruiting Body of Incense Cedar Dry-Rot Fungus. 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. PLATE XII. 




Incense Cedar Wood with Dry Rot. White Mycelium of Fungus 
Visible in the Rot Pockets. 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate XI 




Fresh Fruiting Body of Polyporus schweinitzii. The Light Margin 
Later Becomes a Darker Brown. 

( Photograph by Dr. G. G. Hedgcock.) 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. PLATE XIV. 




Fruiting Bodies of Red Belt Fomes on Western Hemlock, 
i Photograph by Dr. Herman von Schrenk.) 



Forect Tree Diseases, Forest Service, U. S. Dept. of Agriculture. PLATE XV. 




False Tinder Fungus Fruiting Bodies' on Aspen. 

(Photograph by Dr. G. G. Hedgcock.) 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate XVI. 




Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. PLATE XV 1 1 




Indian Paint Fungus Fruiting Bodies, Showing Spiny Undersides. 
(Photograph by Dr. G. G. Hedgeock.) 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. PLATE XVIII 




Indian Paint Fungus in White Fir. 
(Photograph by Dr. G. G. Hedgcock.) 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate XIX. 




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Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. 



Plate XX. 




Forest Tree Diseases, Forest Service, U. S, Dept. of Agriculture. 



Plate XXI 




Mistletoe (Phoradendron juniperinum libocedri) on Incense Cedar. 
Note the Bushes Hanging Downward. 

(Photograph by Dr. G. G. Hedgcock.) 



Forest Tree Diseases, Forest Service, U S. Dept of Agriculture. PLATE XXI 




Forest Tree Diseases, Forest Service, U S. Dept of Agriculture. PLATE XXIII. 




Witches' Brooms Caused by Mistletoe (Razoumofskya campylo- 
foda) on Yellow Pine. 



Forest Tree Diseases, Forest Service, U. S. Dept. of Agriculture. PLATE XXIV. 




Witches' Brooms on Lodgepole Pine Caused by Mistletoe 
(razoumofskya americana). 

(Photograph by Dr. G. G. Hedgcock.) 



INDEX. 



Page. 

Advance rot 28 

Albumen 10 

Annual growth of the tree 8 

Annual rings 8 

Arceuthobium 54 

Armillaria mellea 52 

Bark: 

Diseases 11 

Functions 9 

Black cobweb fungi 38 

Brackets 29 

Cambium 8 

Carbon dioxide, assimilation 10 

Causes of disease 12 

Cloudbursts 16 

Combination of diseases 23 

Conchs 25 

Control of disease 58 

Cortical roots 55 

Decay 26 

Character 40 

Extent 26 

Outward signs 21 

Disease 11 

Diseases of: 

Chinquapin — 

Sulphur fungus 45 

Conifers — 

Black cobweb fungi 38 

Chalky quinine fungus 44 

Honey fungus 52 

Razoumofskya 54 

Red-belt fomes 47 

Ring scale fungus 43 

Root fomes 42 

White pouch fungus 50 

50977°— 14 5 



Page. 
Diseases of — Continued. 

Cottonwood — 

False tinder fungus 49 

Douglas fir — 

Chalky quinine fungus 44 

Indian paint fungus 52 

Mistletoe witches' brooms. 56 

Polyporus schweinitzii 47 

Razoumofskya douglasii ... 57 

Ring scale fungus 43 

Sulphur fungus 45 

Tip-dying 37 

Incense cedar — 

Black cobweb fungi 38 

Dry-rot 46 

Mistletoe swellings 56 

Phoradendron juniperi- 

num libocedri 57 

Rust 35 

Witches' brooms 36 

Jeffrey pine — 

Chalky quinine fungus 44 

Mistletoe witches' brooms . 56 

Pine gall fungus 38 

Razoumofskya campylo- 

poda 57 

Scaly lentinus 53 

Stunting needle fungus 34 

Sulphur fungus 45 

Juniper — 

Phoradendron bolleanum. . 57 

Phoradendron juniperinum 57 

Lodgepole pine — 

Black cobweb fungi 3S 

Chalky quinine fungus 44 

Mistletoe witches' brooms . 56 

65 



66 



FOEEST TEEE DISEASES. 



Diseases of — Continued. Page. 

Lodgepole — Continued. 

Needle fungus 33 

Pine gall fungus 38 

Razoumofskya americana. 57 

Scaly lentinus 53 

Maple — 

Tar-spot fungus 33 

Oak- 
Honey fungus 52 

Hydnum erinaceus 52 

Phoradendron flavescens . . 57 

Polyporus dryophilus 48 

Sulphur fungus 45 

Pines — 

Polyporus schweinitzii 47 

Quaking aspen- 
False tinder fungus 49 

Red fir- 
Black cobweb fungi 38 

Indian paint fungus 52 

Needle disease 33 

Ring scale fungus 43 

Sulphur fungus 45 

Yellow witches' brooms ... 35 

Sugar pine — 

Blue witches' brooms 37 

Chalky quinine fungus 44 

Honey fungus 44,52 

Mistletoe witches' brooms . 56 

Pine gall fungus 38 

Razoumofskya campylo- 

poda 57 

Ring scale fungus 43 

Western service berry — 

Gymnosporangium blas- 

daleanum 36 

White fir- 
Black cobweb fungi 38 

Canker on trunk 58 

Honey fungus 52 

Indian paint fungus 50 

Needle disease 33 

Phoradendron bolleanum . 57 

Polyporus schweinitzii 47 



Diseases of— Continued. Page. 

White fir— Continued. 

Razoumofskya occidentalis 57 

Ring scale fungus 43 

Sulphur fungus 45 

Swellings on trunk 58 

Tip-dying 37 

Top mistletoe 58 

Yellow witches' brooms . . 35 
Willow- 
False tinder fungus 49 

Yellow pine — 

Chalky quinine fungus 44 

Mistletoe witches' brooms . 56 

Needle disease 34 

Pine gall fungus 38 

Razoumofskya campylo- 

poda 57 

Scaly lentinus 53 

Stunting needle fungus 34 

Sulphur fungus 45 

Distortions 31 

Dry-rot of incense cedar 46 

Echinodontium tinctorum 50 

False tinder fungus 49 

Fire ■. 15 

Flowers, diseases 12 

Foliage: 

Diseases 11, 18, 32 

Functions 10 

Fomes annosus 42, 53 

Fomes igniarius 49 

Fomes laricis 44 

Fomes pinicola 47 

Forest hygiene 59 

Forest sanitation 60, 62 

Free use 61 

Frost 16 

Fruiting bodies 25, 28 

Fungi 24 

Gill-bearing fungi 30 

Growth of the tree 8 

Gymnosporangium blasdaleanum . 35 

Heartrot 22, 25, 40 

Character 40 



INDEX. 



67 



Page. 

Heartwood 8 

Diseases 22, 25, 40 

Herpotrichia nigra 38 

Honey fungus 52 

Host 12 

Hydnum erinaceus 52 

Hyphae 25 

Hypoderma 34 

Incense cedar posts 62 

Indian paint fungus 50 

Inferior species 28, 31 

Leaves, diseases 11, 18, 32 

Lentinus lepideus 53 

Lightning 15 

Lophodermium on yellow pine 34 

Lophodermium nervisequium 33 

Mechanical injury 14 

Mineral salts 9 

Mistletoe 54 

Mushrooms 30 

Mycelium 25 

Neopeckia 38 

Normal functions of the tree 9 

Parasites 12 

Peckiness (incense cedar) 46 

Peridermium cerebrum 39 

Peridermium elatinum 35 

Peridermium harknessii 38 

Phoradendron 54, 57 

Phoradendron juniperinum liboce- 

dri 57 

Pitch tubes 23 

Polyporus amarus 46 

Polyporus dryophilus 48 

Polyporus schweinitzii 47 

Polyporus sulphureus 45 

Polyporus volvatus 50 

Porous fungi 29 

Prevention of disease 61 

Ranger sales 61 

Razoumofskya 54, 57 

Red-belt fomes 47 

Resin as protection 31 

Resin flow 21,47,52 

Respiration 10 



Page. 

Rhytisma 33 

Ring scale 43 

Root fomes 42, 44, 52 

Roots: 

Diseases 12, 40 

Functions 9 

Rusty knots 51 

Sanitation clause 62 

Sapwood 8 

Sapwood, diseases 11 

Scaly lentinus 53 

Shelves 29 

Shoe strings , 53 

Sinkers 55 

Smelter fumes 16 

Spiny fungi 29 

Spores 25, 28 

Sporophores 25, 28 

Springwood 8 

Starch 10 

Stools 25 

Storage of food 10 

Stringy brown rot of white fir 50 

Structure of the tree 8 

Sugar 10 

Sulphur fungus 44 

Summerwood 8 

Sunscald 17 

Suppressed trees 27 

Symptoms of disease 18 

Tar-spot fungus 33 

Trametes pini 43 

Transpiration of water 10 

Twigs, diseases 20, 32 

Undesirable trees, use 62 

Water supply of the tree 9 

Whiskered appearance of yellow 

pine 34 

White pouch fungus 50 

Winter injury 16 

Witches' brooms 21 

Wood-destroying fungi 32, 40 

Woodpecker work 23 

Wounds affording entrance to fungi . 12, 40 
Wounds, natural protection 12, 14 



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